A motor control device includes: a power failure detection unit that detects a power failure; a voltage detection unit that detects a DC link voltage; a switch unit which connects a motor to an amplifier or a resistance; a voltage comparison unit which compares a DC link voltage with a threshold value; a limit value setting unit which sets a torque limit value in accordance with a result of comparison; a torque command limit unit which limits a torque command when a power failure is detected; a prediction value calculation unit which calculates, using an angular velocity, a torque prediction value of the motor when the motor is connected to the resistance; and a torque comparison unit which compares the torque limit value with the torque prediction value, in which in accordance with a result of comparison, the switch unit connects the motor to the amplifier or the resistance.

A motor control device includes: a power failure detection unit that detects a power failure; a voltage detection unit that detects a DC link voltage; a switch unit which connects a motor to an amplifier or a resistance; a voltage comparison unit which compares a DC link voltage with a threshold value; a limit value setting unit which sets a torque limit value in accordance with a result of comparison; a torque command limit unit which limits a torque command when a power failure is detected; a prediction value calculation unit which calculates, using an angular velocity, a torque prediction value of the motor when the motor is connected to the resistance; and a torque comparison unit which compares the torque limit value with the torque prediction value, in which in accordance with a result of comparison, the switch unit connects the motor to the amplifier or the resistance.

A servo control apparatus includes a sensor unit for detecting a motor speed; an amplifier for driving a motor and feeding back a current; a magnetic pole position detector; a position controller for outputting a speed command; a speed controller for outputting a current command; a current controller for outputting a voltage command; a speed estimator for calculating an estimated speed from the voltage command; a magnetic pole position estimator for calculating an estimated magnetic pole position from the estimated speed; a sensor malfunction detector; a stop position command generator; and a first switch for switching from the position command to the stop position command, a second switch for switching from the magnetic pole position to the estimated magnetic pole position, and a third switch for switching from the detected speed to the estimated speed, when the sensor malfunction detector has detected a malfunction.

A servo control apparatus includes a sensor unit for detecting a motor speed; an amplifier for driving a motor and feeding back a current; a magnetic pole position detector; a position controller for outputting a speed command; a speed controller for outputting a current command; a current controller for outputting a voltage command; a speed estimator for calculating an estimated speed from the voltage command; a magnetic pole position estimator for calculating an estimated magnetic pole position from the estimated speed; a sensor malfunction detector; a stop position command generator; and a first switch for switching from the position command to the stop position command, a second switch for switching from the magnetic pole position to the estimated magnetic pole position, and a third switch for switching from the detected speed to the estimated speed, when the sensor malfunction detector has detected a malfunction.

A servo control apparatus includes a sensor unit for detecting a motor speed; an amplifier for driving a motor and feeding back a current; a magnetic pole position detector; a position controller for outputting a speed command; a speed controller for outputting a current command; a current controller for outputting a voltage command; a speed estimator for calculating an estimated speed from the voltage command; a magnetic pole position estimator for calculating an estimated magnetic pole position from the estimated speed; a sensor malfunction detector; a stop position command generator; and a first switch for switching from the position command to the stop position command, a second switch for switching from the magnetic pole position to the estimated magnetic pole position, and a third switch for switching from the detected speed to the estimated speed, when the sensor malfunction detector has detected a malfunction.

A servo control apparatus includes a sensor unit for detecting a motor speed; an amplifier for driving a motor and feeding back a current; a magnetic pole position detector; a position controller for outputting a speed command; a speed controller for outputting a current command; a current controller for outputting a voltage command; a speed estimator for calculating an estimated speed from the voltage command; a magnetic pole position estimator for calculating an estimated magnetic pole position from the estimated speed; a sensor malfunction detector; a stop position command generator; and a first switch for switching from the position command to the stop position command, a second switch for switching from the magnetic pole position to the estimated magnetic pole position, and a third switch for switching from the detected speed to the estimated speed, when the sensor malfunction detector has detected a malfunction.

A servo control apparatus includes a sensor unit for detecting a motor speed; an amplifier for driving a motor and feeding back a current; a magnetic pole position detector; a position controller for outputting a speed command; a speed controller for outputting a current command; a current controller for outputting a voltage command; a speed estimator for calculating an estimated speed from the voltage command; a magnetic pole position estimator for calculating an estimated magnetic pole position from the estimated speed; a sensor malfunction detector; a stop position command generator; and a first switch for switching from the position command to the stop position command, a second switch for switching from the magnetic pole position to the estimated magnetic pole position, and a third switch for switching from the detected speed to the estimated speed, when the sensor malfunction detector has detected a malfunction.

A servo control apparatus includes a sensor unit for detecting a motor speed; an amplifier for driving a motor and feeding back a current; a magnetic pole position detector; a position controller for outputting a speed command; a speed controller for outputting a current command; a current controller for outputting a voltage command; a speed estimator for calculating an estimated speed from the voltage command; a magnetic pole position estimator for calculating an estimated magnetic pole position from the estimated speed; a sensor malfunction detector; a stop position command generator; and a first switch for switching from the position command to the stop position command, a second switch for switching from the magnetic pole position to the estimated magnetic pole position, and a third switch for switching from the detected speed to the estimated speed, when the sensor malfunction detector has detected a malfunction.

The motor control system of the present invention includes a signal receiving unit for receiving a signal for operating a mechanical brake, a position monitoring unit for obtaining the history of the rotational position of the servo motor from the receipt of the signal to when the rotation of the servo motor stops using a position detector, a displacement amount calculation unit which calculates the rotational displacement of the servo motor from the receipt of the signal to when the rotation of the servo motor stops from the history, and an abnormality determining unit which determines that an abnormality exists in the mechanical brake when the calculated rotational displacement exceeds a predetermined first threshold value.

A machine tool controller according to an embodiment of the present invention, for controlling a spindle and a feed axis, includes a motor temperature obtaining unit for obtaining and outputting the winding temperature of a spindle motor as a motor temperature; an inverter temperature obtaining unit for obtaining and outputting the temperature of an inverter that drives the spindle motor as an inverter temperature; a motor temperature comparator for comparing the outputted motor temperature with an overheat temperature for the motor; an inverter temperature comparator for comparing the outputted inverter temperature with an overheat temperature for the inverter; and an overheating assessment unit for imposing a restriction on the output of the spindle motor according to the smaller one of the differences between the motor temperature and the overheat temperature for the motor and between the inverter temperature and the overheat temperature for the inverter.